Flotation concentration of phosphate-bearing material



Patented Mar. 3, 1931 UNITED STATES PATE'NT' OFFICE WILLIAM TROTTER, OF NEW YORK, AND ELTOFT WRAY WILKINSON, OI QUEENS 'Vl-I-o- LAGE, NEW YORK, ASSIGNORS TO MINERALS SEPARATION NORTH AIERICAN COR- PORATION, OF NEW YORK, N. Y., A CORPORATION OF MARYLAND FLOTATION CONCENTRATION OI PHOSPHATE-BEARING MATERIAL No. Drawing.

This invention relates to mineral concentration and is herein disclosed as applied to the concentration of phosphate mineral to produce a material rich in Ca P O commercially known as bone phosphate of lime.

It has been known for a long time that some minerals other than metals and metalliferous sulphides are amenable to concentration by the froth-flotation process, but, in the case of phosphates at least, the consumption of agents, principally oil, was so great that the process was unavailable commercially because of the prohibitive cost of the agents in the necessary quantities, particularly when the process is carried out in reclaimed mine pit or washer waters.

According to the present invention these and other difliculties have been overcome. According to the procedures of the present invention the prepared phosphate rock is agitated in a pulp with a suitable soap and with an oily material which may be unsaponifiable or non-frothing, such as fuel oil. Frequently a proportion of one part soap to three parts oil has been found most useful. It is found that relatively coarse phosphate rock, for example, passing 14-mesh, can be floated with a relatively small consumption of such agents and without excessive agitation and aeration, yielding a high grade concentrate and yet with small loss of phosphate in the tailings. The mostsatisfactory results have been obtained within the limits of cost of commercial operations when a substantial reduction of the ordinary proportion of primary slimes was efiected before the prepared rock was submitted to the concentration process. Seeondary slimes resulting from grinding the ore are often so much richer that the increased recovery from them may wholly or partly offset the increased cost of concentration arising from their presence due to increased consumption of soap and oil.

It is not necessary that the concentration Application filed January 24, 1928. Serial 170. 249,197.

haved as if they had some tendency to cohere together and to adhere to the bubbles which had raised them. There were many bubbles in and below the mat which broke on passing through the mat.

lVith finer ground material a froth forms, carrying phosphates in or on its bubble films, but it does not appear to be necessary that much, or in some cases any, froth-flotation concentration be efiected.

Most of the following tests represent work done in testing machines under exactly controlled and reproducible conditions, but parallel results have been obtained in operating an eighteen-inch ten-cell subaeration minerals separation machine, as will also appear.

Undersize phosphate rock from the No. 11 mill of International Agricultural Corporation at Mulberry, Florida, was subjected to a desliming operation until relatively free from slimes and then found to contain little material finer than 100-mesh. It was then screened to remove between five and six per cent of the material which was coarser than 14-mesh Tyler screen. 550 grams of the finer than l t-mesh wet material, carrying about 10 per cent. of water, was agitated in a minerals separation box-type subaeration testing machine with 500 cc. of tap water and there was added, in the order named, 10 cc. of a soap solution and 1.5 cc. of 39 Oklahoma fuel oil.

The soap solution was made by combinin 88 grams single pressed red oil (oleic acid COD- : flowed, with some assistance from a paddle for one minute and forty-five seconds. The concentrate as it lay on the collecting launder was composed of clean grains not unlike wet yellow sea sand. It had practically no trace of the froth films which were obtained with and persisted with the concentrate obtained in treating finer material. The results are shown in terms of bone phosphate of lime in the following table In another test the same material subjected to the same desliming operation, was used. 550 grams were mixed with 500 cc. water. to which was added, in the order named, 10 cc. of a fish-oil soapy emulsion and 3 cc. of the same fuel oil. The fish-oil emulsion was made by warming 25 grams of a dark pressed fisho'il. several years old. with 100 cc. of water and 13 cc. of a 10 per cent. solution of caustic soda. so that 10 cc. of the final solution containcd 1.9 grams of oil and 0.1 grams of caustic soda.

The thick pulp with the emulsion and oil was slowly agitated for 30 seconds. Then water was added to fill the machine almost to overflowing and vigorous agitation started. The float soon rose and over-flowed. A froth of the type usual in froth-flotation appeared only at the end of the frothing period, when the greater part of the phosphate mineral had been removed. The concentrate was removed for two and one-half minutes, and separated by retreatment into a finished concentrate and a middling. The results are shown in the following table:

Recov- Wts. Assays ems Heads 100. 00 47. 1 C0nc 49. 5 79. 0 83. 0 Mid 4. 8 49. 4 6. 0 45. 7 12. 2 11. 9

Another lot of the same material subjected to the same desliming operation, but ground to pass 48-mesh and 61 per cent. passing 150- mesh, and carrying all the slime formed in grinding, was concentrated asfollows:

500 grams of the dry material was slowly mixed with 500 cc. of waterand there was added 25 cc. of a 5 per cent. solution of pure sodium olcatc and 5 cc. of fuel oil. After one minute enough water was added to fill the machine and vigorous agitation started. The float was collected during 1% minutes. The first float was a heavy froth concentrate in which'bubble films survived when separated from the pulp. The concentrate was retreated to give a finished concentrate, and a middling. The results are shown in the followmg table:

Recov- Wt. Assays mes A pulp of phosphate pebble screenings of the Mulberry Florida, mine passing approximately QO-mesh was subjected to a desliming operation until relatively free from slimes and was concentrated by feeding at the rate of about nine tons of solids per hour through a ten-cell \Vilkinson and Littleford subaeration impeller flotation machine with the addition at the first-cell of sodium oleate 3.9 pounds and fuel oil 12.4 pounds, both per ton of solids, together with a very small quantity of pine oil. Only enough water was used in the first two cells to make an easily mixed pulp, estimated to contain solids. Enough water was added at the third cell to make a pulp estimated to contain 17% of solids, and the float was removed in this and later cells.

The heads contained 39.4% bone phosphate of lime, the concentrates 71% and the tailings 10.2% making a commercial yield, with a recovery of 86.5%.

In one continuous mill run about 65 to tons of similar material passing about 28- mesh was subjected to a desliming operation until it contained a Very small proportion of slimes. It was agitated in a thick pulp with 4.9 pounds of oleic acid soap and 8.06 pounds of Mexican fuel oil, both per ton of solids. The feed contained 29.22% bone phosphate of lime. The pulp was thinned, further agitated, and a concentrate was concentrated separately yielding rough concentrates and rough tailings, and final concentrates, middlings and final tailings, havremoved for one and one-half minutes. The results are shown in the following table:

ing the contents of bone phosphate of lime gg i Recoveries shown in the following table: Pwdu" per c'ent limoper cent per can ASSiiySp6I' cent Heads 100. 30.30

. 35.0 72.71 11.2 1.0 47.80 9.1 Noretreatment Ratreated T5115 12-22 Tail- Mid Other phosphate ores require some modifications in treatment. It 1s found that very '33:: gg @2 3 22:: :2 smallamounts of silicate of soda may be g3 3% 4 3.; sometimes advantageously added to the pulp, especially after the addition of the other The agents used were 6 pounds of sodium oleate and 18 pounds of Oklahoma fuel oil, both per ton of solids, and, except for the addition of a further 2 pounds of sodium oleate, perton of solids in treating the 100-mesh material, no agents were added for retreating the materials.

Other tests indicated that much less soap and oil would have yielded an equally good result with the coarser materials.

Addition of the soap and oil to a thick pulp containing as much as 60% solids and disseminating by agitation thereof and thereafter thinning to yield a float frequently proves economical, partly because less of the soap is consumed in softening the water, partly because less oil seems to be needed when the smaller quantity of soap is used, and partly because less equipment is needed, though useful results may be obtained by agitating in the freely flowing pulp which was to yield the float. Satisfactory dissemination was obtained in a pulp so thick that it would barely flow down a 30 grade, until later diluted for flotation.

In one test run the crude phosphate ore passing 20 mesh was subjected to a desliming operation until free from primary slimes. The subaeration machine was started slowly with 400 cc. of water, and then was added 500 grams of the crude phosphate ore, so that of 0.12 pounds, all per ton of solids. The machine was then brought up to full speed for 15 seconds, then slowed and water added to make a freely flowing pulp containing 17% solids. The speed was then increased and air admitted so that a float rose, and this float was removed for three minutes. The tailings were removed, the concentrates put back in the machine with 0.12 pounds additional pine oil per ton of original ore, water added to nearly fill the machine, agitation resumed, air admitted and the finished concentrates agents. Other bubble-forming agents than pure soap have been found helpful in the presence of soap, such as cresol or the pine oil mentioned above or the sulphonated castor oil known as Turkey red oil. Many other soaps, have been satisfactorily used, such as cotton-seed oil soap, laundry soaps, borax soaps and rosin-containing soaps, but one pure cocoanut oil soap gave no useful result. Saponified rosin in one test proved useless. The exact nature of the soap makes some difference in the results, and freshly prepared soaps sometimes proved best. Moreover commercial soaps sometimes proved more satisfactory than the chemically pure soaps.

Microscopic examination of the prepared phosphate rock showed that its gangue was mainly transparent silica and that the binding of silica to phosphate was Well destroyed in the 14-mesh material.

Having thus described certain embodiments of the invention, what is claimed is:

1. The process of concentrating phosphatebearing material which consists in subjecting such material to a desliming operation, then agitating and aerating a pulp of the material with oil and with a compound adapted to control selective oiling of the phosphate so as when cooperating with such oil to yield a floating concentrate, and separating the float.

2. The process of concentrating phosphatebearing material which consists in agitating and aerating atpulp of the material with soap and a non-frothing oil so as to yield a floating concentrate, and separating the float.

3. The process of concentrating phosphatebearing material which consists in subjecting such material to a desliming operation, then agitating and aerating a pulp of the material with soap and oil so as to yield a floating concentrate, and separating the float.

4. The process of concentrating phosphatebearing material which consists in agitating and aerating a pulp of the material with soap and petroleum oil so as to yield a floating concentrate, and separating the float.

5. The process of concentrating phosphatebearing material which consists in subjecting suchmaterial to a desliming operation, YT

then agitating and aerating a pulp of the material with soap and oil in the proportion of about one to three, the soap being used in about that proportion to the area of the surfaces of the particles of phosphate material which two pounds bears to the surfaces of twenty-mesh material, the agitation and aeration being so conducted as to yield a floating concentrate, and separating the float.

6. The process of concentrating phosphate bearing material which consists in subjecting such material to a desliming operation so that it is practically free from sizes coarser than l i-mesh, then agitating and aerating a pulp of the material with soap and fuel oil so as to yield a floating concentrate, and separating the float.

7. The process of concentrating phosphatebearing material Which consists in subjecting such material to a desliming operation to yield floatable sizes-containing a minimum of slimes then agitating and aerating a pul of the material with soap and oil so as to yield a floating concentrate, and separating the float.

8. The process of concentrating phosphatebearing material which consists in agitating with soap and petroleum oil a pul of the material which is too thick to flow reel so that the phosphate is selectively oiled, dlluting the pulp with water to make a freel flowing pulp, agitating and aeratingthe (i iluted pulp to produce a floating concentrate, and separating the float.

9. The process of concentrating phosphatebearing material which consists in subjecting such material to a desliming operation, then agitating with soap and petroleum oil, in the proportion of about one to three, a pulp of the material which is too thick to soap being used in about that proportion to the area of the surfaces of theparticlesof phosphate material which two pounds bears to the surfaces of twenty-mesh material, diluting the pulp with water to make a freely-flowing pulp, agitating and aerating the diluted pulp to produce a floating concentrate, and separating the concentrate. J

10. The process of concentrating phosphate-bearing material containing gangue, which consists in subjecting such material to a desliming operation, then agitating and aerating a pulp of the material with oil and with a compound adapted to control selective oiling of the phosphate so as to effect the lifting in the pulp of 'p'hosphate-bearin particles above gangue particles by attached air bubbles, and collecting phosphate-bearing particles relatively free from gangue particles.

11. The process of concentrating ph0sphate-bearing material containing gangue, which consists in agitating and aerating a pulp of the material with sea and a nonfrothing oil so as to efl'ect the in the flow freely, the

pulp of phos hate-bearing particles above gangue partic es by tively free from gangue partic es.

12. The process of concentrating phosphate-bearing material containing gan e, which consists'in agitating with soap and p etroleum oil a u? of the material which is too thick to flow reely so that the phosphate 1s selectively oiled, diluting the ulp with water to make a freely-flowing p p, agitatmg and aerating the effect the lifting in the pulp of phosphatebearing particles above gangue particles, and collecting phosphate-bearing articles relatively free from gangue partic es.

In testimonywhereof, we have aflixed our signatures to this specification.

WILLIAM TROTTER. ELTOFT WRAY WILKINSON.

attached air bubbles, and collecting phosphate-bearing articles reladiluted pulp so as to 

